When the yeast is added to the hydrogen peroxide it acts as a catalyst to release the extra oxygen gas. The soap is used to make it foamy.

First an adult should add a small amount of Hydrogen Peroxide into an empty liter bottle (clean used soda bottle can be used). Then add 1 tablespoon of yeast into a cup with water - mix it. Add a few drop of dish soap into the 1 liter bottle with the hydrogen peroxide along with a few drop of food coloring.

Once the dry yeast is well mixed in the water, with safety glasses on, pour it into the liter bottle containing the hydrogen peroxide.